| ECOLOGY |
UV triggers NOx emissions from pine trees Exposure to ultraviolet rays causes pine trees to emit nitrogen oxides (NOx), according to a study carried out in Finland. The reactive trace gases are key players in atmospheric chemistry, playing a role in smog formation, for example. Plants are usually considered a sink for NOx, not a source. But Pertti Hari, professor of forest ecology at the University of Helsinki, and coworkers now suggest that global NOx emissions from northern forests could rival those from traffic and industry [Nature, 422, 134 (2003)]. The researchers measured NOx flux from Scots pine shoots enclosed in special chambers. The shoots released NOx when the chambers were covered with quartz glass that allows UV light from the sun to penetrate, but not when covered with a UV-opaque plastic. The origin of the emitted NOx is unclear, the scientists note. The magnitude of the flux is large enough to affect the atmospheric NOx budget, they conclude |
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